1. Field of the Invention
This invention relates to a portable autonomous device for the detection and recording, during relatively long periods of time, of magnitudes representative of randomly occurring phenomena of short duration.
It applies notably, but not exclusively, to the detection and recording of shocks capable of affecting objects such as goods, during transportation and/or handling thereof.
Of course, such a detection can notably serve to subsequently reveal the cause of a deterioration of the object monitored and the moment (time stamping) at which the shock that caused this deterioration occurred. This information enables e.g. determination of who is responsible for the damage thus caused and can therefore constitute elements that are particularly useful to insurance companies, or even to the law.
It is clear that within the scope of such an application, a device of this type must have considerable autonomy, while having as small a bulk as possible. Moreover, it must be perfectly tight, shock-resistant and be capable of operating under difficult conditions (high and low temperatures). It must also be completely inviolable (the memorized information must only be read by autorized persons and must be protected against all forms of destruction).
2. Description of the Prior Art
Given these imperatives, continuous detection of the magnitude to be monitored and periodical memorizing of samples representative of this magnitude are excluded. In fact, the power consumption specific to this type of operating is relatively high and does not enable both good autonomy and a low volume to be obtained.
This is due to the fact that even in the case where one has, for the detection of the magnitudes to be measured, sensors that consume little electrical power (such as e.g. the capacitive accelerometers used for the detection of the shocks), the microcontroller necessarily used to ensure the operating sequences consumes too much electricity when operated continuously.
With a view to solving this problem, the invention works from the observation that in the applications concerned by the invention, the phenomena to be detected:
do not occur frequently (in theory, they should not occur at all), PA1 occur during a relatively short though not inconsiderable period of time.